The project involves the analysis of developing function in the immature primate prefrontal cortex. Infant and juvenile Rhesus monkeys are trained to perform a delayed response task which requires short term memory for positional cues. This task is known to be an indicator of prefrontal function in the mature animal. Utilizing local, reversible cooling adapted to chronic unanesthetized animals, we are able to examine the effects of temporary cryogenic depression of prefrontal cortex at various times during each animal's period of maturation. Due to known connections between prefrontal cortex and two subcortical regions, the nucleus medialis dorsalis and the caudate nucleus, we are also examining the development of prefrontal influences on the latter two structures by the use of subcortical single unit recording in conjunction with prefrontal cooling. In addition to tracing of afferent and efferent connections of recording sites with immunoperoxidase localization of injected horseradish peroxidase and autoradiographic visualization of injected (3H)-leucine, further work will include single unit recording from infant prefrontal cortex during behavioral performance.